The world population graph is misleading. Looking at it one could be lead to believe that in 2100 there will be 13bln people.

In reality by 2100 the world's population will be around 10.2bln and declining from 10.3bln in 2084 or so.

And that also assumes the UN won't revise its projections once again, as every time they did, they had to lower their estimates.